The present invention relates to an apparatus for printing a fluid material by means of a continuous jet printing technique, comprising a reservoir for storing the material; an outflow surface comprising at least one outflow opening in fluid connection with the reservoir, from which outflow opening, in use, flows a jet of the material breaking up into drops; pressure generating means arranged for applying a pressure on the reservoir for passing the material under pressure from the reservoir in the direction of the outflow opening; a pressure regulating mechanism comprising an actuating surface arranged near the outflow opening for providing pressure variations of the material by means of vibration of the actuating surface for the purpose of obtaining a controlled breakup of the jet into drops.
In this connection, by “a continuous jet printing technique” is meant the continuous generation of drops which can be utilized selectively for the purpose of a predetermined printing process. The supply of drops takes place continuously, in contrast to the so-called drop-on-demand technique whereby drops are generated according to the predetermined printing process.
Document EP 1,545,884 B1 discloses a known apparatus for printing a fluid material by means of a continuous jet printing technique. To achieve a controlled breakup of the jet into drops, a sufficiently large pressure regulating mechanism is provided in front of the outflow opening. In the printing of fluids having a particularly high viscosity, work is done at an average relatively high pressure in the channel, e.g. in a range between 15 and 600 bar. To achieve a high regulating range for typical pressures the known apparatus of EP 1,545,884 B1 is provided with a pressure regulating mechanism comprising a movable control pin wherein an end of the control pin is placed at a predetermined distance in the distance interval of 15-500 μm from the outflow opening. Due to the distances in the distance interval being relatively small, a relatively large pressure regulating range can be realized. The known method of reducing the distance interval of the control pin to achieve satisfactory pressure variations at the outflow opening may have limits, e.g. because the control pin gets too close to the nozzle plate comprising the outflow opening and/or due to increasing stresses on the control pin and or other parts of the apparatus.
There is yet a need for continuous printing of materials with higher viscosities and/or at higher rates than currently possible.